Error When Detection First Launch (Swift)

Question

I am trying to detect if the app is being opened for the first time. I've put this piece of code in my ViewController's viewDidLoad()

override func viewDidLoad() {
        super.viewDidLoad()

        let launchedBefore = UserDefaults.standard.bool(forKey: "launchedBefore")
        if launchedBefore  {
            performSegue(withIdentifier: "toMainController", sender: self)
            print("launchedBefore")
        } else {
            performSegue(withIdentifier: "toTutorialController", sender: self)
            UserDefaults.standard.set(true, forKey: "launchedBefore")
            print("not launchedBefore")

        }
    }

But, whenever the ViewController launches, no segues are performed. But thext I told it to print, is printed. If it matters, the view that the segue "toMainController" goes to is a UITabViewController, and the view that the segue "toTutorialController" goes to is just a UIViewController.

Does anyone have any ideas why this isn't working?

UPDATE

I found this error

2017-06-30 09:02:32.984 AppName[29732:24744712] Warning: Attempt to present on < AppName.ViewController: 0x7fcbfa908ed0> whose view is not in the window hierarchy!

Add the above code after **UserDefaults.standard.set(true, forKey: "launchedBefore")** — Vignesh Davins, Jun 30 '17 at 12:50
Possible duplicate of [How to check if the IOS app is running for the first time using SWIFT](https://stackoverflow.com/questions/30635160/how-to-check-if-the-ios-app-is-running-for-the-first-time-using-swift) — Vignesh Davins, Jun 30 '17 at 12:53
@VigneshDavins In swift 3 you do not need `synchronize`, and method after `performSegue` will be executed — Fangming, Jun 30 '17 at 12:54
Have you checked if your segues are setup corectly in IB? What happens if you move this code to `viewDidAppear`? — Losiowaty, Jun 30 '17 at 12:56
If the text is printed the error is related to the segues and the associated controllers. — vadian, Jun 30 '17 at 13:05
@VigneshDavins Check out my update. I found some more information. — Jacob Cavin, Jun 30 '17 at 13:06

score 1 · Answer 1 · answered Jun 30 '17 at 13:02

First save in userDefault and then perform segue:-

override func viewDidLoad() {
        super.viewDidLoad()

        let launchedBefore = UserDefaults.standard.bool(forKey: "launchedBefore")
        if launchedBefore  {
            performSegue(withIdentifier: "toMainController", sender: self)
            print("launchedBefore")
        } else {
            UserDefaults.standard.set(true, forKey: "launchedBefore")
            performSegue(withIdentifier: "toTutorialController", sender: self)
            print("not launchedBefore")
        }
    }

score 1 · Answer 2 · answered Jun 30 '17 at 13:26

override func viewDidLoad() {
        super.viewDidLoad()
      DispatchQueue.main.async {
        let launchedBefore = UserDefaults.standard.bool(forKey: "launchedBefore")
        if launchedBefore  {
            performSegue(withIdentifier: "toMainController", sender: self)
            print("launchedBefore")
        } else {
            UserDefaults.standard.set(true, forKey: "launchedBefore")
            performSegue(withIdentifier: "toTutorialController", sender: self)
            print("not launchedBefore")
        }
    }
  }

score 0 · Answer 3 · answered Jun 30 '17 at 13:16

0

I figured it out. The problem wasn't the code itself, it was just where it was being executed. It needed to be executed in the UITabBarViewController.

answered Jun 30 '17 at 13:16

Jacob Cavin

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Error When Detection First Launch (Swift)

3 Answers3